python · StanFromIreland · May 9, 2026 · May 9, 2026
diff --git a/Doc/deprecations/pending-removal-in-3.16.rst b/Doc/deprecations/pending-removal-in-3.16.rst
@@ -89,7 +89,7 @@ Pending removal in Python 3.16
 
 * :mod:`sys`:
 
-  * The :func:`~sys._enablelegacywindowsfsencoding` function
+  * The :func:`!sys._enablelegacywindowsfsencoding` function
     has been deprecated since Python 3.13.
     Use the :envvar:`PYTHONLEGACYWINDOWSFSENCODING` environment variable instead.
 

diff --git a/Doc/library/sys.rst b/Doc/library/sys.rst
@@ -879,7 +879,7 @@ always available. Unless explicitly noted otherwise, all variables are read-only
 
    .. versionchanged:: 3.6
       Windows is no longer guaranteed to return ``'mbcs'``. See :pep:`529`
-      and :func:`_enablelegacywindowsfsencoding` for more information.
+      for more information.
 
    .. versionchanged:: 3.7
       Return ``'utf-8'`` if the :ref:`Python UTF-8 Mode <utf8-mode>` is
@@ -2107,31 +2107,6 @@ always available. Unless explicitly noted otherwise, all variables are read-only
       See :pep:`768` for more details.
 
 
-.. function:: _enablelegacywindowsfsencoding()
-
-   Changes the :term:`filesystem encoding and error handler` to 'mbcs' and
-   'replace' respectively, for consistency with versions of Python prior to
-   3.6.
-
-   This is equivalent to defining the :envvar:`PYTHONLEGACYWINDOWSFSENCODING`
-   environment variable before launching Python.
-
-   See also :func:`sys.getfilesystemencoding` and
-   :func:`sys.getfilesystemencodeerrors`.
-
-   .. availability:: Windows.
-
-   .. note::
-      Changing the filesystem encoding after Python startup is risky because
-      the old fsencoding or paths encoded by the old fsencoding may be cached
-      somewhere. Use :envvar:`PYTHONLEGACYWINDOWSFSENCODING` instead.
-
-   .. versionadded:: 3.6
-      See :pep:`529` for more details.
-
-   .. deprecated-removed:: 3.13 3.16
-      Use :envvar:`PYTHONLEGACYWINDOWSFSENCODING` instead.
-
 .. data:: stdin
           stdout
           stderr

@@ -7,4 +7,5 @@ c-api/file.html: deprecated-api
 library/asyncio-task.html: terminating-a-task-group
 
 # Removed APIs
-library/symtable.html: symtable.Class.get_methods
+library/symtable.html: symtable.Class.get_methods
+library/sys.html: sys._enablelegacywindowsfsencoding
diff --git a/Doc/using/cmdline.rst b/Doc/using/cmdline.rst
@@ -1154,9 +1154,6 @@ conflict.
    'replace', respectively.  Otherwise, the new defaults 'utf-8' and
    'surrogatepass' are used.
 
-   This may also be enabled at runtime with
-   :func:`sys._enablelegacywindowsfsencoding`.
-
    .. availability:: Windows.
 
    .. versionadded:: 3.6

@@ -1958,7 +1958,7 @@ New Deprecations
 
 * :mod:`sys`:
 
-  * Deprecate the :func:`~sys._enablelegacywindowsfsencoding` function,
+  * Deprecate the :func:`!sys._enablelegacywindowsfsencoding` function,
     to be removed in Python 3.16.
     Use the :envvar:`PYTHONLEGACYWINDOWSFSENCODING` environment variable instead.
     (Contributed by Inada Naoki in :gh:`73427`.)

@@ -126,6 +126,14 @@ symtable
 * The :meth:`!symtable.Class.get_methods` method
   which has been deprecated since Python 3.14.
 
+sys
+---
+
+* The :func:`!sys._enablelegacywindowsfsencoding` function
+  which has been deprecated since Python 3.13.
+  Use the :envvar:`PYTHONLEGACYWINDOWSFSENCODING` environment variable instead.
+  (Contributed by Stan Ulbrych in :gh:`149595`.)
+
 sysconfig
 ---------
 

@@ -517,7 +517,7 @@ Applications that do not use str to represent paths should use
 :func:`os.fsencode` and :func:`os.fsdecode` to ensure their bytes are
 correctly encoded. To revert to the previous behaviour, set
 :envvar:`PYTHONLEGACYWINDOWSFSENCODING` or call
-:func:`sys._enablelegacywindowsfsencoding`.
+:func:`!sys._enablelegacywindowsfsencoding`.
 
 See :pep:`529` for more information and discussion of code modifications that
 may be required.

@@ -18,9 +18,6 @@ extern int _Py_SetFileSystemEncoding(
     const char *errors);
 extern void _Py_ClearFileSystemEncoding(void);
 extern PyStatus _PyUnicode_InitEncodings(PyThreadState *tstate);
-#ifdef MS_WINDOWS
-extern int _PyUnicode_EnableLegacyWindowsFSEncoding(void);
-#endif
 
 extern int _Py_IsLocaleCoercionTarget(const char *ctype_loc);
 

diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
@@ -1283,16 +1283,6 @@ def check(tracebacklimit, expected):
     def test_no_duplicates_in_meta_path(self):
         self.assertEqual(len(sys.meta_path), len(set(sys.meta_path)))
 
-    @unittest.skipUnless(hasattr(sys, "_enablelegacywindowsfsencoding"),
-                         'needs sys._enablelegacywindowsfsencoding()')
-    def test__enablelegacywindowsfsencoding(self):
-        code = ('import sys',
-                'sys._enablelegacywindowsfsencoding()',
-                'print(sys.getfilesystemencoding(), sys.getfilesystemencodeerrors())')
-        rc, out, err = assert_python_ok('-c', '; '.join(code))
-        out = out.decode('ascii', 'replace').rstrip()
-        self.assertEqual(out, 'mbcs replace')
-
     @support.requires_subprocess()
     def test_orig_argv(self):
         code = textwrap.dedent('''

diff --git a/Misc/NEWS.d/3.13.0a3.rst b/Misc/NEWS.d/3.13.0a3.rst
@@ -2166,7 +2166,7 @@ current user has no permission to the WMI.
 .. nonce: WOpiNt
 .. section: Windows
 
-Deprecate :func:`sys._enablelegacywindowsfsencoding`. Use
+Deprecate :func:`!sys._enablelegacywindowsfsencoding`. Use
 :envvar:`PYTHONLEGACYWINDOWSFSENCODING` instead. Patch by Inada Naoki.
 
 ..

diff --git a/Misc/NEWS.d/next/Library/2026-05-09-11-22-29.gh-issue-149595.1nuYXw.rst b/Misc/NEWS.d/next/Library/2026-05-09-11-22-29.gh-issue-149595.1nuYXw.rst
@@ -0,0 +1,2 @@
+Remove the :func:`!sys._enablelegacywindowsfsencoding` function which has
+been deprecated since Python 3.13.
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
@@ -14928,33 +14928,6 @@ _PyUnicode_FiniEncodings(struct _Py_unicode_fs_codec *fs_codec)
 }
 
 
-#ifdef MS_WINDOWS
-int
-_PyUnicode_EnableLegacyWindowsFSEncoding(void)
-{
-    PyInterpreterState *interp = _PyInterpreterState_GET();
-    PyConfig *config = (PyConfig *)_PyInterpreterState_GetConfig(interp);
-
-    /* Set the filesystem encoding to mbcs/replace (PEP 529) */
-    wchar_t *encoding = _PyMem_RawWcsdup(L"mbcs");
-    wchar_t *errors = _PyMem_RawWcsdup(L"replace");
-    if (encoding == NULL || errors == NULL) {
-        PyMem_RawFree(encoding);
-        PyMem_RawFree(errors);
-        PyErr_NoMemory();
-        return -1;
-    }
-
-    PyMem_RawFree(config->filesystem_encoding);
-    config->filesystem_encoding = encoding;
-    PyMem_RawFree(config->filesystem_errors);
-    config->filesystem_errors = errors;
-
-    return init_fs_codec(interp);
-}
-#endif
-
-
 #ifdef Py_DEBUG
 static inline int
 unicode_is_finalizing(void)

diff --git a/Python/clinic/sysmodule.c.h b/Python/clinic/sysmodule.c.h
@@ -1790,36 +1790,6 @@ sys_getwindowsversion_impl(PyObject *module)
 }
 
 #pragma warning(pop)
-
-/*[clinic input]
-sys._enablelegacywindowsfsencoding
-
-Changes the default filesystem encoding to mbcs:replace.
-
-This is done for consistency with earlier versions of Python. See PEP
-529 for more information.
-
-This is equivalent to defining the PYTHONLEGACYWINDOWSFSENCODING
-environment variable before launching Python.
-[clinic start generated code]*/
-
-static PyObject *
-sys__enablelegacywindowsfsencoding_impl(PyObject *module)
-/*[clinic end generated code: output=f5c3855b45e24fe9 input=2bfa931a20704492]*/
-{
-    if (PyErr_WarnEx(PyExc_DeprecationWarning,
-        "sys._enablelegacywindowsfsencoding() is deprecated and will be "
-        "removed in Python 3.16. Use PYTHONLEGACYWINDOWSFSENCODING "
-        "instead.", 1))
-    {
-        return NULL;
-    }
-    if (_PyUnicode_EnableLegacyWindowsFSEncoding() < 0) {
-        return NULL;
-    }
-    Py_RETURN_NONE;
-}
-
 #endif /* MS_WINDOWS */
 
 #ifdef HAVE_DLOPEN
@@ -2941,7 +2911,6 @@ static PyMethodDef sys_methods[] = {
     SYS__GETFRAME_METHODDEF
     SYS__GETFRAMEMODULENAME_METHODDEF
     SYS_GETWINDOWSVERSION_METHODDEF
-    SYS__ENABLELEGACYWINDOWSFSENCODING_METHODDEF
     SYS__IS_IMMORTAL_METHODDEF
     SYS_INTERN_METHODDEF
     SYS__IS_INTERNED_METHODDEF
@@ -3436,13 +3405,6 @@ winver -- [Windows only] version number of the Python DLL\n\
 "
 )
 #endif /* MS_COREDLL */
-#ifdef MS_WINDOWS
-/* concatenating string here */
-PyDoc_STR(
-"_enablelegacywindowsfsencoding -- [Windows only]\n\
-"
-)
-#endif
 PyDoc_STR(
 "__stdin__ -- the original stdin; don't touch!\n\
 __stdout__ -- the original stdout; don't touch!\n\
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Remove the :func:`!sys._enablelegacywindowsfsencoding` function which has
		been deprecated since Python 3.13.